Timaru's Sally Betts has a constantly evolving family.

One student, Dorothy, moved in five years ago after Betts offered.

It's the first place she's lived in consistently: "Dorothy's here forever really," Betts said.

And she's not the only one; Betts never says no to visitors.

"It's not hard, just opening your home," she said. "Doors are made to be opened, always."

The teenagers come from nearby Roncalli College, where Betts is Year 13 dean and head of food and hospitality.

At the school, Betts has the students making chemotherapy care packages for people in cancer treatment.

Betts has suffered from breast cancer herself.

Principal Chris Comeau said: "I haven't met many people like Sally who has not opened just her doors, but opened her heart.

"She doesn't see Dorothy as just a boarder, but she sees Dorothy as another member of her family."